Gai's base feats are much better, handling Obito's cqc Kamui better than KCM Naruto, without Gates enhancement and while worn out, is >>> forcing Itachi back (Itachi could still fend and dodge his hits) amd defeating Sasuke, who could anyway keep up with Bee's kenjutsu for the most part. Gai opens some Gates and kicks V1/V1 Bee's shit. When Bee goes full Hachibi, Gai goes 7th Gate, blitzes and unleashes a couple of Hiru Tora on his face, one after another, knocking him out; 6th Gate Gai with a couple of jumps makes all the giant Kumo turtle island, so dodging Bijuu Dama is not a problem, and the Hachibi can't react to his movement and attack speed.
8th Gate would be an unholy rape.